The wire reeler or pin hub disclosed here is designed to be used in conjunction with interchangeable wire reels or reel cartridges. In use, an empty reel is mounted via a robotic arm to a pin hub constructed in accordance with the present invention. Thereafter, the leading end of a continuous wire is fed from a feed station and is clamped directly to the reel. This is followed by driving the pin hub in rotation, which correspondingly drives the reel in rotation, and draws the wire from the feed station and winds it into a coil about the reel. The pin hub rotates until a selected length or segment of the wire is wound onto the reel. Then, the wire is clamped and cut, thereby severing it from the feed station and defining the aft end of the coiled segment.
The reel carries the clamps required for holding the leading and aft ends of the wire segment described above. Further details of the clamping and winding operation will be described in later portions of this document as they are germane to the invention.
After winding, cutting and clamping the segment as just described, the robotic arm removes the reel from the pin hub, and transports it for storage or use elsewhere. Another empty reel is then placed by the arm on the pin hub, and the winding process is repeated, but for a new segment.
The pin hub disclosed here is a further development made in conjunction with an automated wire harness assembly system that is presently under development by The Boeing Company. As is well known, Boeing is a manufacturer of passenger jets, and other, related aerospace products.
Large numbers of wire harnesses are used in the manufacture of commercial jets. These harnesses are typically made up of bundles of individual wire segments having varying lengths. Traditionally, they are assembled or bound together by hand. Such assembly is, of course, extremely labor intensive, and significant cost savings could be achieved if such process were automated.
For this reason, Boeing has long been involved in the in-house development of an automated system for producing wire harnesses. A portion of the system presently under development by Boeing is disclosed in U.S. Pat. No. 4,803,778, which was identified above. The present invention is related to the subject matter of the '778 patent, but more particularly, it is meant to replace the wire reeler disclosed in U.S. Pat. No. 4,520,966 (the '966 reeler), which was also identified above.
During the course of further research and development, it became apparent that the '966 reeler had certain drawbacks, or that other improvements or changes to the automated system as a whole required a new reeler design. As was discussed in the specification of the '966 patent, it was a design goal to produce transportable wire canisters having the capability of accepting, storing and later dispensing individual wire segments during the automated assembly of a wire harness. It is now estimated that an automated system may require a separate reel or wire cartridge for each wire segment, and that literally thousands of individual segments will be processed should an automated harness manufacturing system eventually be implemented. Given the apparently large numbers involved, the '966 canister is too large and cumbersome to be of practical use. In comparison, the hub design disclosed here, which is to be used in combination with an improved reel design (the latter being the subject of my co-pending application Ser. No. 07/892,153) eliminates some, if not all, of the '966 canister's drawbacks.
An important goal of the Boeing system is to use robotic handling devices as much as possible. It is relatively easy to use a robotic arm for the purpose of placing and/or removing a wire reel to and from a pin hub. In contrast, it is difficult to design an automated way to guide the leading end of the wire from a feed station into a clamp on the reel, although it is believed that the reel design which is the subject of my co-pending application makes that particular problem solvable. Nevertheless, further technical problems are presented at the end of the operation, i.e. clamping and severing the aft end of the segment, because the other clamp on the reel most likely will not be in the correct clamping position or location at the time winding stops.
Since the length of each wire segment will typically vary from one reel to the next, the number of rotations of the pin hub required for each winding operation will also vary. The end result is that the particular reel clamp whose function is to capture the wire, prior to severing it from the feed station, will not be in the appropriate angular position when winding stops. Therefore, it is likely that further rotation of both the pin hub and reel will be required in order to properly position the clamp, but at the same time, such rotation must occur without taking up more wire from the feed station, or otherwise subjecting the wire to an unacceptable amount of tension.
Furthermore, in an automated system, when a wire segment is wound onto a reel, and there is to be subsequent automated processing of one or both ends of the segment (e.g., gripping a segment end for removing insulation, or for attaching an end connector), it is necessary that both segment ends be in a known geometric position. Otherwise, other automated equipment would not be able to access the ends for subsequent processing. Therefore, when winding stops, and the aft-end clamp is not in the appropriate "home" position, the pin hub and reel must permit further rotation to "home" without affecting what will ultimately be the segment end geometry.
Different approaches have been used by others in an attempt to solve the above-described problems. For example, the Vectronics Corp. of San Diego, Calif., has used a wire reel or handler that has opposing flexible sides with lips that close over the segment as it enters into an enclosed space. After winding, the coiled segment, if allowed to slacken, cannot escape the enclosure defined by the reel. When the aft end of the segment is reached during the winding process, the Vectronics reel is rotated to an angular "home" position by rotating the reel backwards the necessary angular amount. Such rotation is made possible because the internally-coiled wire goes slack due to the backward rotation, and the closed lips just described above prevent the slack wire from escaping from the reel. The known drawbacks to this design are that it does not adequately contain the wire as it slackens, and further, it does not provide the capability of rotating in both directions.
Another known approach to the "home" position problem is to use only one, forward direction of rotation at all times, with a special hub known in the field as a "magic hub". This type of wire handler has a small, fixed inner hub (approximately 1 inch in diameter) and a larger outer hub (approximately 2.5 inches in diameter) that is formed by flexing one hub sidewall in closing contact against another, opposite sidewall. During the winding process, the wire segment is initially reeled onto the outer hub while it is in a closed position. In other words, the wire is wound while the hub sidewalls are closed. When the second or aft end position of the wire arrives, the hub is then relaxed, which opens a gap between the sidewalls down to the fixed, inner hub. This enables the hub to be rotated further in the same direction until the home position is reached, and the slack required for such further rotation is provided by pulling some of the coils of the already wound segment into the gap region between the two hubs.
The "magic hub" method has its own, unique drawbacks. First, it is highly complex, and thus creates higher costs in view of the very large number of wire handlers or reels that will be needed for an automated handling system. Second, when the leading end and initial portion of small gauge wire types are reeled under tension onto such hub, they tend to be pulled between the contacting sidewalls of the outer hub and down onto the inner hub. This can make it difficult to later attain the "home" position. Lastly, there is no positive way to assure that the initial turns of the wire segment around the outer hub will be sufficiently aligned over the gap, when it is subsequently created, in order to assure that at least some coils will move down onto the inner hub when the gap is opened.
As will become apparent, the present invention enables further rotation of a reel into the "home" position without pulling more wire from the feed station, or otherwise placing the wire under an undue amount of tension. The invention also enables rotation in either direction, in order to efficiently clamp the aft end of each segment prior to severing it from the feed station. Lastly, the invention enables predetermined lengths of wire segments to be reeled onto a maneuverable reel device where both ends of the wire are maintained in known geometric positions for subsequent processing in an automated harness assembly system.
In addition to the above, a pin hub in accordance with the invention provides a reel-drive mechanism that is under the control of the mechanism which drives the wire-reeling process. Only a single pin hub is required for winding various individual segments onto any number of different reels. This makes wire handling much more cost effective as a whole, because the cost of the hub is but for a single unit, and is independent of the cost of producing the numerous reels that would be required in order to process the large number of wire segments that are presently anticipated. In conjunction with cost, inspection and maintenance is made much easier with the present pin hub, because only a single reeler device must be inspected, as opposed to many.
How the invention functions to solve the above-described problems and to provide the above-described advantages will become apparent to the skilled person upon consideration of the disclosure which follows.